The present invention relates to a developer apparatus for electrophotographic printing. More specifically, the invention relates to a filter for filtering toner.
In the well-known process of electrophotographic printing, a charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as “toner.” Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced.
The toner image may then be transferred to a substrate or support member (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
In the process of electrophotographic printing, the step of conveying toner to the latent image on the photoreceptor is known as “development.” The object of effective development of a latent image on the photoreceptor is to convey developer material to the latent image at a controlled rate so that the developer material effectively adheres electrostatically to the charged areas on the latent image.
In an electrophotographic printer as the toner material is transferred to the photoreceptor and eventually to the copy paper, this used toner must be replaced. The electrophotographic printer thus includes one or both of a device for recapturing toner cleaned from the charge retentive surface and a device for replenishing toner from which fresh toner is dispensed into the machine.
Several devices are known for filtering recycled toner cleaned from the charge retentive surface. U.S. Pat. No. 5,200,788 discloses a brush auger reclaim filtration assembly incorporated into an open ended chamber. The brush auger is a toner reclaim filtration device that is rotatably mounted, in the chamber, to move toner and debris along a separating screen. Also contained in the housing is a mounted transport auger that rotates as it moves the reclaimed toner to the development housing.
U.S. Pat. No. 4,389,968 discloses a toner regenerating device with a mesh disposed in the route of the toner collected from an image bearing member. The device includes an apparatus for imparting to the collected toner through the mesh a force causing the collected toner to move along the mesh. The collected toner on the mesh containing foreign material and solidified toner is loosened so that the solidified toner is divided into fine particles. The foreign matter is caused to float up over the collected toner and prevented from passing through the mesh. The device includes a transporter for carrying toner to and into a chamber through a first opening. Toner in the chamber is moved out of a second opening. An elastic plate is mounted at one of its ends for rotation within the chamber such that its opposite tip end is maintained in contact with the interior wall of the chamber except at the second chamber opening.
U.S. Pat. No. 4,054,381 discloses a toner filter arrangement adapted for use in a cleaning station of a electrophotographic reproduction machine. Foreign material and other contaminants are removed from residual toner prior to its collection in a disposable or reuse container or return to the developer station. The filter arrangement comprises a housing having an input opening through which removed toner enters and an output opening through which filtered toner exits. The housing includes a spiral brush mounted for rotation on a shaft centrally located within the housing and a stationary open mesh screen coaxially located with respect to the shaft. Rotation of the brush operates to sift toner through the screen to the outlet of the filter housing.
In earlier copy machines and printers, toner used in the developer unit was replenished by pouring loose toner into a toner container. In using this replenishing method at least two major problems occurred. The first problem was that a portion of the loose toner could either be spilled during filling or the loose toner would form a cloud when filling and settle later. In either case the spilled or settled toner could contaminate the machine or printer and require an expensive service call. The second problem was that contamination could enter the toner container during fill and negatively affect the operation of the machine. U.S. Pat. No. 4,561,759 discloses a device for filling and filtering toner from a supply container which is placed by an operator in communication with a feed container in a photocopier. The device has a cylindrical filling opening for the feed container with a cross section such that the supply container can be inverted. The device has a filter basket disposed in the region of the filling opening which is closed from the feed container by a filter mesh. An electric vibrator is connected to the device.
In more recent copy machines and printers, toner used in the developer unit is replenished by exchanging an empty toner replenishment cartridge with a new, full replenishment cartridge. Many devices have been used to seal the replenishment cartridge prior to installation in the machine. These devices and others have been used to maintain the sealed integrity of the replenishment cartridge during the exchange of an empty replenishment cartridge for a full replenishment cartridge. The use of replenishment cartridges has reduced the problems with spilled and settled toner as well as contamination problems during toner replenishing. To provide for a small compact replenishment cartridge and to provide for a replenishment cartridge in which the opening to the replenishment cartridge may be easily removed, the replenishment cartridge typically has a compact shape with a small opening from which at least toner is dispensed.
While the use of replenishment cartridges for the storage and refilling of toner within a machine reduces the contamination encountered during filling, even in the most stringently controlled manufacturing environments, contaminants may enter the toner itself during its manufacture and/or could enter the replenishment cartridge during filling at the factory and later progress into the developer housing causing copy quality problems. If the contamination, particularly in the form of fibers or oversized materials (debris, flakes, etc.), reaches the developer housing, copy quality and machine reliability suffer.
The development system, the area of the electrophotographic printer where the toner is transferred to the photoreceptor, typically includes a wide area extending across the full width of the photoreceptor in order that a full image width may be developed. The toner must thus progress from the replenishment container into the developer housing and progress along the full width of the developer housing in order that the full width of the latent image may be developed. Furthermore, in attempts to make inexpensive and compact electrophotographic printers and to minimize space and related costs, the location of the toner replenishment cartridge and the developer housing may be far apart.
To aid in transferring toner in the developer housing to the photoreceptor, the toner particles are often mixed with carrier particles. The use of smaller carrier and toner particles, which are typical when using colored toners for color electrophotography compounds problems associated with contamination. Imperfections in color copies, such as those caused by contamination, are often more noticeable to the human eye than imperfections in monochromic copies.
The presence of contamination in development systems utilizing hybrid scavengeless development is particularly a concern. The purpose and function of scavengeless development are described more fully in, for example, U.S. Pat. No. 4,868,600 to Hays et al., U.S. Pat. No. 4,984,019 to Folkins, U.S. Pat. No. 5,010,367 to Hays, or U.S. Pat. No. 5,063,875 to Folkins et al. U.S. Pat. No. 4,868,600 is incorporated herein by reference.
In a scavengeless development system, toner is detached from a donor roll by applying AC electric field to self-spaced electrode structures, commonly in the form of wires positioned in the nip between a donor roll and photoreceptor. This forms a toner powder cloud in the nip and the latent image attracts toner from the powder cloud thereto. Because there is no physical contact between the development apparatus and the photoreceptor, scavengeless development is useful for devices in which different types of toner are supplied onto the same photoreceptor such as in “tri-level”; “recharge, expose and develop”; “highlight”; or “image on image” color electrophotography. The small color toner and related carrier particles used for the implementation of these devices and the greater visual scrutiny given to color copies compound contamination problems. Furthermore, the electrode wires utilized to form the toner powder cloud are particularly susceptible to contamination in general and in particular, to contamination from fibers or oversized materials (debris, flakes, etc.).
One familiar type of development of an electrostatic image is called “two-component development”. Two-component developer material largely comprises toner particles interspersed with carrier particles. The carrier particles are magnetically attractable, and the toner particles are caused to adhere triboelectrically to the carrier particles. This two-component developer can be conveyed, by means such as a “magnetic roll,” to the electrostatic latent image, where toner particles become detached from the carrier particles and adhere to the electrostatic latent image.
U.S. Pat. No. 4,614,165, assigned to the assignee hereof, discloses the general principle of what is known familiarly as “trickle” development. Very briefly, trickle development involves providing two distinct supplies of toner and carrier particles. The first supply, referred to herein as developer material, is initially present in the developer housing. The developer unit draws toner from the developer material for application to the electrostatic latent image. The second supply of toner and/or toner and carrier particles, referred to herein as replenisher or a replenishment supply, is separate from the developer material and is often present in a replenishment bottle, hopper, cartridge or other container. The replenishment supply is used to replenish the first supply over time by adding toner or toner and carrier particles as the toner or toner and carrier particles are depleted from the first supply. Thus, upon introduction into the developer housing the toner or toner and carrier particles of the replenishment supply become toner and carrier particles of the development material. Typically, the developer material and replenishment supply have substantially different ratios of toner to carrier.
Many printer systems are sensitive to oversized particle contamination in the developer housing. Toner flakes made during the normal toner filling process, as well as fibers or oversized materials (debris, flakes, etc.) already present in the bottle received from the manufacturer, may cause image quality problems, such as streaking of the printed output, in such sensitive printer systems. Currently oversized contamination issues are addressed minimizing or eliminating fibers or oversized materials (debris, flakes, etc.) introduction or formation in the toner manufacturing and filling process. Also, manufacturers attempt to address oversized contamination issues by attempting to eliminate any sources of foreign contamination in the empty bottles during their assembly process.
In addition to, or instead of, the above described filtering systems, users of electrostatographic printing systems would appreciate a filter for filtering toner or toner and carrier as it is removed from a replenishment supply.
The disclosure describes a method and device for containing oversized toner and contaminant flakes within a replenishment supply, such as a replenisher bottle, during use. The disclosed method and device inhibit fibers or oversized materials (debris, flakes, etc.) from entering the replenisher dispense system within the printer system. This reduces the number of streaks that the printer system experiences improving customer satisfaction. The disclosed apparatus utilizes an internal screen to inhibit oversized materials (debris, flakes etc.) from exiting the replenishment supply during use. The screen covers the opening of the auger of the replenisher dispense system that is used by the machine to extract replenisher from the replenishment supply, thereby inhibiting these particles from leaving the replenishment supply and being introduced into the developer material.
According to one aspect of the disclosure, an apparatus for developing an electrostatic latent image employed in a printing machine comprises a photoreceptor, a developer unit, a replenisher supply source, a replenisher transporter and a filter. The photoreceptor is configured to receive a latent image thereon, to attract toner particles to the latent image and to transfer attracted toner particles to a substrate. The developer unit is positioned relative to the photoreceptor to permit toner to be transferred to the photoreceptor. The developer unit includes a developer housing defining a chamber containing an initial supply of developer material including toner particles and a toner transfer system for transferring toner particles present in the housing to the photoreceptor. The replenisher supply source contains replenisher comprising toner particles. The replenisher transporter is in communication with the replenisher supply source through an opening and in communication with the chamber of the developer housing for transporting replenisher from the replenisher supply source to the chamber of the developer housing. The filter is disposed between the replenisher supply source and the chamber of the developer housing. The filter is configured to limit the size of particles discharged from the replenisher supply source and entering the chamber of the developer housing.
According to another aspect of the disclosure, a replenisher cartridge for supplying replenisher to a developer unit of an electrophotographic printing machine comprises a container, a supply of replenisher and a filter element. The container is configured for communication with a replenisher transporter communicating with a chamber of the developer unit. The replenisher transporter has an opening for communicating with the interior of the container. The supply of replenisher comprises toner disposed in the container. The filter element is disposed relative to the opening to filter replenisher passing through the opening.
According to yet another aspect of the disclosure, a method of providing replenisher for replenishing development material utilized in developing an electrostatic latent image recorded on a photoconductive member employed in an electrophotographic printing machine including a replenisher transporter is disclosed. The method includes several steps not necessarily performed in the order presented unless otherwise indicated. In an opening step, a filtered replenisher cartridge is opened. The replenisher cartridge includes a seal cap for sealing an opening through which the cartridge communicates with the replenisher transporter when the seal cap is dislodged from the opening and a portion of the replenisher transporter is received through the opening and a filter for filtering particles entering the replenisher transporter. The opened filtered replenisher cartridge has been removed from an electrophotographic printing machine including a replenisher transporter. The method also includes a filling step wherein the replenisher cartridge is filled with replenisher comprising toner particles. The method also includes a positioning step wherein the seal cap is positioned to seal the opening through which the cartridge communicates with the replenisher transporter
Additional features and advantages of the presently disclosed filter for toner particles will become apparent to those skilled in the art upon consideration of the following detailed description of embodiments exemplifying the best mode of carrying out the disclosed apparatus as presently perceived.
Corresponding reference characters indicate corresponding parts throughout the several views. Like reference characters tend to indicate like parts throughout the several views.